This invention relates to a process for preparing 7-(1-hydroxyethyl)-3-(2-aminoethylthio)-1-carbadethiaceph-3-em-3-carboxyli c acid and its pharmaceutically acceptable salts and esters (I) which are useful as antibiotics: ##STR2## The compound of Structure I might for convenience be called "homothienamycin" on reference to the known antibiotic thienamycin III: ##STR3## Homothienamycin (I) is disclosed and claimed in co-pending, commonly assigned U.S. Patent Application Ser. No. 903,455 (filed May 8, 1978) now U.S. Pat. No. 4,150,156 issued Apr. 17, 1979 which is incorporated herein by reference to the extent that it describes I and its utility as an antibiotic. Also incorporated by reference is U.S. Pat. No. 3,950,357 which discloses and claims thienamycin; this patent is incorporated by reference to the extent that it teaches the utility of antibiotics such as III and by analogy I.
The process of the present invention is a total synthesis, starting with L-aspartic acid and proceeding in a stereo-selective manner via intermediate II. ##STR4## wherein R is a conventional protecting group. The details of the total synthesis are given below.